A light source with a luminescence conversion element is disclosed, for example, in WO 97/50132. It comprises a semiconductor chip which, during operation, emits primary radiation of which part is converted into light of a different wavelength by the luminescence conversion element. The resulting, optically perceivable radiation from the light-emitting diode light source is given by a mixture of the two radiations, so that, as a result, in particular light sources which also emit white light can be produced. The luminescence conversion material has at least one light-emitting material which is embedded in a matrix material.
There are a plurality of known methods for arranging the luminescence conversion material within the path of light emission from the light-emitting diode chip. One possibility is to mix light-emitting material with a potting compound, as described for example in the Laid-Open Specification WO 98/12757. The light-emitting diode chip is in this case mounted on a pre-housed leadframe and is then covered with the wavelength-converting potting compound. The color locus of light (CIE color chart) that is emitted from light-emitting diode light sources produced in accordance with such a process can vary even though such light sources are produced in the same way. The causes for this can be sedimentation formation of the light-emitting material in the potting compound or different thicknesses of the luminescence-converting potting compound over the light-emitting diode chips.
Such problems can be eliminated to some extent by light-emitting diode chips mounted on a leadframe being encapsulated in a luminescence conversion compound, as shown for example in DE 199 63 806 A1. In this case, when a molding technique is used for the light-emitting material, use can be made of a molding compound with a higher viscosity, which cures more quickly. As a result, sedimentation formation of the light-emitting material occurs to a lesser extent. In addition, by means of such a production process, it is possible to dispense with a prefabricated housing, which means a considerable ability to miniaturize light-emitting diode light sources.
As a result of using a mold, light-emitting diode light sources of the same overall height are obtained. However, this leads to luminescence conversion layers of different thicknesses on the chips since, even in the case of light-emitting diode chips from the same wafer composite, it is possible for height fluctuations to occur of, for example, up to 20 μm. A further disadvantage of molding techniques is high production costs since, with high investment costs for the installation and tools, there is only a low yield per production cycle.